Retractable bed

ABSTRACT

A retractable bed having a first frame supported off the floor by a high-low mechanism and a second frame slidably mounted on the first frame. A mattress frame, having a head section, seat section, and leg section which includes thigh and foot sections, is supported on the second frame with the seat section rigidly attached to the second frame. An actuating mechanism is provided for pivoting the head section to permit the patient to be moved from a prone position to a sitting position and vice versa, while at the same time moving the second frame and the mattress frame towards or away from the headboard of the bed, to thereby keep the patient&#39;&#39;s head and shoulders at substantially the same horizontal distance from the end of the bed.

United States Patent [72} Inventors Robert Knight Etobicoke, Ontario;Stanley Rachlinski, Oakville, Ontario, both of, Canada '[21] Appl. No.806,880 [22] Filed Mar. 13,1969 [45] Patented July 20, 1971 [73]Assignee The Dominion Metalware Industries Limited Port Credit, Ontario,Canada [54] RETRACTABLE BED 45 Claims, 6 Drawing Figs.

[52] U.S. Cl l t 5/66, 5/68 [51] Int. Cl A6lg 7/10, A61 g 7/00 [50]Field of Search 5/63, 6669 [56] References Cited UNITED STATES PATENTS3,216,026 11/1965 Mann 5/66 Primary ExaminerCasmir A. NunbergAttorney-Rogers, Bereskin & Parr ABSTRACT: A retractable bed having afirst frame supported off the floor by a high-low mechanism and a secondframe slidably mounted on the first frame. A mattress frame, having ahead section, seat section, and leg section which includes thigh andfoot sections, is supported on the second frame with the seat sectionrigidly attached to the second frame. An actuating mechanism is providedfor pivoting the head section to permit the patient to be moved from aprone position to a sitting position and vice versa, while at the sametime moving the second frame and the mattress frame towards or away fromthe headboard of the bed, to thereby keep the patients head andshoulders at substantially the same horizontal distance from the end ofthe bed.

PATENTED JUL20 l9?! SHEET 1 BF 5 [NV/5N]! )RS ROBERT KNIGHT STANLEYRACHLINSKI PATENTEO JUL20 l9?! sum 20F 5 INVIQNYHRS ROBERT KNIGHTSTANLEY RACHLINSKI PATENIEU JULZOISH sum 3 OF 5 [NV/3N! HRS ROBERTKNIGHT STAN LEY RACH Ll NSKI PATENTEnJuLeomn 3593350 SHEET k [1F 5 FIG.5

LOWER Nfl/TRAL LOWER 140 Y 22 LE6 5667/0 co/vmaz HEAD SECTION con/m0;

INVILN'HWS ROBERT KNIGHT BY STANLEY RACHLINSKI 2?, awk, 12

PATENTED JUL 20 I9?! SHEET 5 BF 5 N i ,w-

INVENIYIRS ROBERT KNIGHT STAN LEY RACH Ll NSKI yal, 4' 3w RETRACTABLEBED This invention relates to beds and in particular to a retractablehospital bed.

It is customary to provide hospital beds with numerous adjustableelements to improve patient comfort, to facilitate nursing care, and toassist in the treatment of certain medical conditions. For example, theheight of the bed usually is adjustable between high and low positions.When the bed is in its high position, it is easier for the nurse to carefor the patient, and when it is in its low position it is easier for thepatient to get into and out of bed. A bed incorporating this feature iscommonly referred to as a high-low" bed. Other adjustments are commonlyprovided to allow a mattress frame to hinge at a number of points alongits length so that the patient can be supported in various positions,such as a sitting position, Trendelenberg position, and reverseTrendelenberg position. A typical bed incorporating these adjustmentshas a seat section attached to a main frame of the bed, a head section,and a leg section, the head and leg sections respectively beingpivotally secured to the seat section on opposite sides thereof. The legsection includes a thigh section and a foot section pivotally secured tothethigh section. The foot and thigh sections usually are coplanar whenthe bed is in the Trendelenberg or reverse Trendelenberg positions, butof course they may be pivoted to an appropriate degree when the patientis in a sitting position with his legs bent somewhat.

When the head section is tilted to support a patient in the sittingposition, his head and shoulders are further away from the head end ofthe bed than they are when he is in a prone position. This relativemovement of the patients head and shoulders often causes the patientsome difficulty in reaching switches and personal effects placed inbedside cabinets and the like, which are usually positioned for easyaccess in one position of the patient and therefore are somewhat out ofposition when the patient is in the other position.

Objects of the present invention are to provide an improved bed having amattress frame which automatically retracts towards the head end of the.bed as the head section is elevated, which can easily beadjusted intothe various'positions described above, and which is reliable, sturdy,and relatively economical to manufacture.

A preferred form of the present bed consists of a main or first framespaced from the floor, preferably supported bya high-low mechanism ofthe kind described in Canadian Pat. No. 728,839, and a second frameslidably mounted on the first frame. A mattress frame, having a headsection seat section, and leg section (including thigh and footsections) is sup ported on the second frame with the seat sectionrigidly attached to the second frame. An actuating mechanismis providedfor pivoting the head section to pennit the patient to be moved from aprone position to a sitting position and vice versa, while at the sametime moving the second frame and the mattress frame towards (or awayfrom) the headboard of the bed, to thereby keep the patients head andshoulders at sub stantially the same horizontal distance from the end ofthe bed.

In drawings illustrating a preferred embodiment of the invention,

FIG. I is a perspective partially exploded view of an improvedretractable bed;

FIG. 2 is a sectional view of the bed in the horizontal, or normal,position;

FIG. 3 is a sectional view of the bed showing the mattress frame inposition for supporting a patient in a sitting position;

FIG. 4 is a diagrammatic sectional view of the bed showing the legsection of the mattress frame in various positions;

FIG. 5 is a somewhat diagrammatic perspective view of a control systemfor use with the bed; and

FIG. 6 is a sectional view through an actuating mechanism used inperforming various adjustments.

Referring to FIG. I, an improved retractable bed I consists of arectangular main or first frame 4 supported by a high-low mechanism 2,and a rectangular second frame 6 slidably mounted on the first frame 4to allow longitudinal motion of the second frame 6 relative to the firstframe 4. Supported on the second frame 6 is a generally rectangularmattress support frame 8 consisting of a head section 56, a seat section58, a thigh section 60, and a foot section 62 hingedly connected inseriatim. The seat section 58 is fixed to the second frame 6, the othersections being free to pivot. A head-section-actuating mechanism 10 ismounted in a trunnion 42 on the second frame 6 and is adapted to tiltthe head section 56 about pivot points 64 attached to the seat section58 and contemporaneously to slide the second frame 6 along the firstframe 4 towards a headboard 31. A leg-section-actuating mechanism 14 isalso mounted on the second frame 6 and it is adapted to lift the thighsection 60 about pivot points 66.

The first frame 4 consists of a pair of longitudinal members 23connected by a series of transverse members 22 and is provided withvertical standards 27 to which the headboard 31 and a footboard 33 aresecured. The high-low mechanism 2 which is similar to the apparatusdescribed in Canadian Pat. No. 728,839 consists of a lower frame 25supported on wheels 18 and it has parallel links 20 pivotally mountedonthe frame 25 at points 24. A pair of axles 29, each having a link 20rigidly attached at each end, is pivotally supported on the underside ofthe main fi'ame at pivot points 26 and a pair of parallel cranks 30 arerespectively fixed to the axles 29 and interconnected with a pushrod 28pivotally secured at its ends to the cranks 30. A cylindrical housing 32is secured to a trunnion 36 on a transverse member 22, and it houses anactuating mechanism (described in detail below with reference-to FIG. 6)which is driven by a reversible electric motor 34 for impartinglongitudinal movement to the pushrod 28. The high-low mechanism 2utilizes the longitudinal motion of the 28 to raise and lower the firstframe 4.

The second frame 6 consists of a pair of longitudinal members 45 spacedapart by a pair of transverse members 44. Two trunnion support bars 48are respectively fixed to each of the longitudinal members 45 and eachis strengthened by a bar 49 which extends between an adjacent transversebar 44 and the trunnion support bar 48. The longitudinal members 45 eachhave a pair of wheels or rollers 54 secured to the outside face of themembers 45. The wheels 54 are constrained within U- sectioned tracks 46secured to the longitudinal members 23.

The head-section-actuating mechanism 10 is mounted on trunnion bolts 42(one of which is shown) and it is contained within a cylindrical housing40. The mechanism 10 (described in detail below with reference to FIG.6) is operated by a reversible motor 38 and is adapted to move a rod 41longitudinally inwards and outwards. As the rod 41 moves it operates asystem of interconnected rods and cranks to lift the head section 56 asfollows.

A pair of identical brackets 70 are respectively attached to oppositesides of the head section 56 and a first rod 72 and a second rod 76extend between them. A crank 74 is fixed to the rod 72 and is pivotallyconnected at its distal end to the distal end of the rod 41. As thecrank 74 rotates, the actuating mechanism 10 rocks in trunnion bolts 42.A pair of identical cranks 78 and 79 are fixed to the second rod 76 andare pivotally connected at their distal ends to one end of identicalradius arms 80 and 81 which respectively are pivotally supported inbrackets 82 and 83 on transverse member 22. The position of the secondframe 6 relative to the first frame 4 is determined by the angle of theradius arms 80 and 81 with respect to the longitudinal axis of the bed.

When the head section 56 of the mattress frame 8 is in a horizontalposition as shown in FIG. 1, it is supported by a frame 84 formed with agenerally horizontal portion 86, and two generally vertical portions 88which terminate in horizontal portions 90 which constitute stops. Theframe 84 is pivotally connected to the longitudinal members 23 at pivotpoints 92 and is normally balanced in the position shown in FIG. I withthe stop portions 90 abutting the standards 27. A handle 94 is used tomove the frame84 towards the headboard pushrod 31, as indicated by arrow95, so that the head section 56 may pivot downwardly to provide theTrendelenberg position. A slot 47 in the rod 41 allows the head section56 to so move without pulling on the rod 41.

FIGS. 2 and 3 illustrate the position of the headsection-actuatingmechanism and its associated parts when the head section 56 is in ahorizontal position (FIG. 2) and a raised position (FIG. 3). The headsection 56 is raised by the actuation of the motor 38 which causes therod 41 to extend outwardly from the housing 40 and thereby operate thecrank 74 through pin 43. The crank 74, rod 72, brackets 70 and headsection 56 are all welded together to form an integral unit. Since theunit is hinged at 64 to a pair of similar supports 59 (only one of whichis shown) which forms part of the second frame, and the mechanism 10 isalso mounted on the second frame, all of the movement of the rod 41 isused to move the head section 56 upwardly about the pivot points 64.

Longitudinal motion of the second frame 6 relative to the first frame 4is possible only if the radius arms 80 and 81 describe an arc abouttheir lower pivot points. Referring to F IG. 3, when the mechanism 10causes the head section 56 to rotate about the pivots 64 in thedirection of arrow 65, the radius arms 80, 81 rotate in the direction ofarrow 67. The projected horizontal length of the arms 80 and 81 in theposition shown in FIG. 2 is longer than the projected horizontal lengthof the same arms in the position shown in FIG. 3 because they areobviously at a steeper angle in FIG. 3. Since the radius arms 80 and 81control the position of the second frame 6 relative to the first frame4, the second frame 6 must move towards the headboard 31 in order tocompensate for the change in projected length of the arms 80 and 81.Arrow 69 (FIG. 3) indicates the movement of the second frame and itsassociated parts. Thus, when the head section 56 of the bed is raisedits leading edge 57 maintains almost exactly the same horizontalposition, i.e. directly above the support frame 84. The patient's headand shoulders thus remain at substantially the same distance away fromthe headboard 31 during raising and lowering of the head section 56.

[n the bed shown in the drawings, the head-section-actuating mechanism10 is secured to the second frame 6. However, the head-sectionactuatingmechanism 10 may be secured to the first frame 4 if required. It wouldthen be necessary to lengthen the rod 41 on the actuating mechanism 10since the second frame 6 moves relative to the first frame 4 and thismovement must be taken up by the rod 41. It is therefore preferable tomount the mechanism 10 on the second frame 6 so that the length of therod 41 can be kept to a minimum. The mechanism 10 could also be securedto the main frame 4 near the headboard 31 or below the transverse member22. The rod 41 would then act directly on the leading edge 57 of thehead section 56 of the mattress frame 8. However, this arrangement hasthe disadvantage that it may interfere with the high-low motion, andmake the bed less attractive.

FlGS. 1, 3 and 4 illustrate the operation of the leg-sectionactuatingmechanism 14. Referring to FIG. 1 a reversible motor 50 and cylindricalhousing 52 similar to that of the head-section-actuating mechanism 10 issupported in a trunnion 53 and operates a rod 51 longitudinally inwardsand outwards. The thigh section 60 is hingedly connected at pivot points66 to the seat secton 58, and a pair of identical plates 93 which areconnected rigidly by a rod 96 are fixed to the thigh section 60 onopposite sides thereof. A crank 98 is rigidly connected to the rod 96and is pivotally connected at its distal end by a pin 55 to the distalend of the rod 51. The pin 55 forms part of a control mechanism morefully described below with reference to FIG. 5. The thigh section 60 ofthe mattress frame 8 is pivoted at pivot points 68 to the foot section62. A rod 100 carries a pair of rigidly connected cranks 102 and isfixed at its end to the foot section 62. The foot section 62 issupported by a pair of parallel notched bars 104 which are pivotallyconnected to the cranks 102. The notched bars 104 can be pivoted intovarious angular positions by engagement of their notches with a U-shapednotch-engaging member 112. The parallel notched bars 104 each have aroller or wheel 108 rotatably secured at their distal ends and the U-shaped bar 112 is pivotally attached at pivot points 110 to the footsection 62. The U-shaped bar 112 has a generally horizontal portion 116for engagement with the notches of the notched bars 104. A transversebar 106 fixed at its ends to the notched bars 104 keeps them parallel toeach other. The rollers 108 are sufficiently far apart to allow them torun on the upper surfaces of the longitudinal members 23, and they areguided by legs 107 which slide on the outer faces of the longitudinalmembers 23. The foot section 62 may be lowered into the reverseTrendelenberg position by lifting the foot section 62 and U-shapednotch-engaging bar 112, and then lowering the foot section 62 with thenotch-engaging bar 112 against the transverse member 106 (this positionis not shown in the drawings).

H68. 2 and 4 illustrate the thigh section 60 and foot section 62 andtheir associated parts in a horizontal position (partially shown in FIG.2) and a raised position (FIG. 4). To move the thigh section 60 upwardlyas shown in FIG. 4, the electric motor 50 is activated, thereby causingthe rod 51 to withdraw into the housing 52. The crank 98, rod 96 andplates 93 are rigidly connected and turn as a unit about the pivotpoints 66 as the rod 51 moves inwardly. The foot section 62, notchedbars 104, and U-shaped notch-engaging bar 112, pivot as a unit about thepivot points 68 while moving in the direction of arrow 120 (FIG. 4). Atypical position of the foot section 62 is shown in FIG. 4 in solidoutline. If it is required to raise the foot section 62 further, thenurse can lift the foot section 62 manually to the desired extent andthe notch-engaging bar 112 then falls into the nearest notch, therebylocking the foot section 62 in position (e.g. the position shown inchain-dotted outline in FIG. 4). It is preferable to lower the footsection 62 back to the position shown in solid outline in FIG. 4 beforelowering the thigh section 60 with the aid of the motor 50. This willensure that the bed returns to the flat horizontal position shown inFIG. 2. Movement of the thigh section 60 does not result in movement ofthe second frame 6 relative to the first frame 4.

The motor 50, housing 52, and associated internal parts are similar tothe motor 38, housing 40 and its associated internal parts. Theoperations described above require the rod 41 of thehead-section-actuating mechanism 10 to move away from the motor 38, andthe rod 51 of the leg-section-actuating mechanism 14 to move towards themotor 50, when the head sections 56 and the thigh section 60 are raisedfrom their horizontal positions shown in FIG. 2. However, since both ofthese operations are reversible, the actuating mechanisms can beidentical.

The actuating mechanisms described in detail below are controlled asfollows. Referring to FIGS. 1 and 5, a pair of control levers 122 and124 extend through openings in the supports 59 for the seat section 58(see FIG. 1) and they control the movement of the head and thighsections respectively. The head section control lever 122 (FIG. 5) isshown in raise" position; the other positions are neutral and lower." Acontrol bar 126 is integrally formed with the lever 122, and it has apair of cranks 130 and 131 rigidly attached to it. A control rod 134 ispivotally attached at one end to the distal end of the crank 130 and ispivotally attached at its opposite end to a switch-actuating plate 144.A support pillar pivotally supports the switch-actuating plate 144. Theswitch-actuating plate 144 can move from a first position where it abutsagainst a stop 153, to a second position (not shown) where it abutsagainst a stop 152. These positions of the switch-actuating plate 144respectively correspond to the raise" and lower" positions shown for thelever 122. When the lever 122 is in the neutral" position theswitch-actuating plate 144 is midway between the stops 153 and 152. Aswitch 146 for activating the electric motor 38 is connected through aswitch lever 155 to the switchplate 144 so that as the switchplate 144is moved by the lever 122 it sets the switch 146 in one of threepositions corresponding to the "raise,"

neutral and lower" positions of the lever 122. The switch 146 is a SPDT(single pole double throw) toggle switch with a center off" position.

When the lever 122 is moved from the neutral position to the raiseposition (arrow 158a), it causes the crank 130 to move in the directionof arrow 158b so that the rod 134 moves in the direction of arrow 158aand causes the switchplate 144 to rotate in the direction of an arrow158d until it hits the stop 153. One circuit of the switch 146 thereuponcloses, thereby actuating the motor 38 which results in movement of rod41 in the direction of arrow 158e. The rod 41 has a pair of stops 138and 140 adjustably secured to it. If the lever 122 is left in the raiseposition, the stop 140 eventually engages the crank 131 and turns thelever 122 back to the neutral" position. The resulting motion of the rod134 returns the switch 146 to its center off position, thereby stoppingthe motor 38. The operation is similar when the lever 122 is placed inthe lower position. In this case the stop 138 will return the lever 122to the neutral position when it engages the crank 131. In the lowerposition, the direction of the arrow 1582 is reversed.

The leg section control lever 124 is shown in the raise position in H6.5. A control bar 128 is rigidly attached to the lever 124 and it has acrank 132 rigidly attached to it. A control rod 136 is pivotallyconnected at one end to the distal end of the crank 132 and is pivotallyconnected at its other end to a switch-actuating plate 142, similar toswitch'actuating plate 144. A SPDT center off switch 148 is linked tothe switchactuating plate 142 in the same way as the switch-actuatingplate 144 is linked to the switch 146. A second control rod 137 ispivotally connected at one end to the switch-actuating plate 142 and ithas a parallel-sided rigid loop 139 at its other end. The pin 55 on therod 51 pivotally connects the rod 51 to crank 98, and slides freelywithin the loop 139.

When the lever 124 is moved from the neutral" to the raise" position(arrow 160a), it rotates the crank 132 in the direction of arrow [60bthereby causing the rod 136 to move in the direction of arrow 160e, andcausing the switch-actuating plate 142 to rotate in the direction ofarrow 160d. One circuit of the switch 148 thereupon closes, thusactivating the motor 50 (FIG. 1) and causing the rod 51 to move in thedirection of arrow 160a (FIG. 5). 1f the lever 124 is left in the raiseposition, the rod 51 will carry the pin 55 along the loop 139 until thepin 55 engages the closed end of the loop 139 nearest theswitch-actuating plate 142. The rod 51 will continue to move until thepin 55 has pushed the rod 137 sufficiently to move the switch 148 intothe off position. The motor 50 then stops and the thigh section is thenin the maximum raised position. When the lever 124 is moved into thelower position, the same operation occurs except that the direction ofthe arrows 160 is reversed. The pin 55 will then pull the free end ofthe loop 139 to move the switch 148 to the off" position.

The purpose of the stops 138, 140 and loop 139 is to automatically limitthe travel of the rods 41 and 51 respectively. However, the movement ofthe rods 41 and 51 (and hence the inclination of the head and thighsections) can be stopped at any time by moving the levers 122 and 124into the neutral position.

The levers 122 and 124 are duplicated on the other side of the bed (notshown in the drawings). A control box 16 houses the switches 146, 148and associated parts and is positioned on any convenient portion of thesecond frame 6.

The head-section-actuating mechanism (which is identical to thethigh-section-actuating mechanism 14 and the highlow actuatingmechanism) is shown in F IG. 6. The reversible motor 38 drives a shaft174 through a right-angle reduction gearbox 172. Bearings 184 and 188support the shaft 174. The lower end of the rod 41 is provided with arigidly attached recirculating ball nut 176, and is threadably connectedto a portion 190 of the shaft 174. The whole assembly is mounted on atrunnion 180 and trunnion block 182 which also supports the bearing 184.When the motor 38 is energized, the shaft 174 rotates, and the rod 41moves linearly outwards due to the relative rotation between the nut 176and the shaft 174'. The rod 41 must be restrained to prevent it fromturning (e.g. by slidably attaching it to a link or crankwhich formspart of the associated mechanism). Slot 47 through the rod 41facilitates connection of the rod 41 to the associated parts. Thecomplete actuating mechanism can be removed from the bed bydisconnecting the trunnion 180, electrical connections to the motor 38,and the pin through the slot 47. The trunnion allows the actuatingmechanism 10 to compensate for changes in height of the pin 43 (FIG. 3)which follows a circular path about the pivot point 64.

What we claim as our invention is:

1. A hospital bed comprising:

a. a first frame having head and foot ends and parallel,

spaced-apart longitudinal members;

b. means supporting said frame above a floor and parallel thereto;

c. a mattress support frame having a head section and a seat section,said head section being pivotally connected to said seat section;

d. means slidably supporting said mattress support frame above saidfirst frame, said supporting means being adapted to permit said mattresssupport frame to slide longitudinally relative to said first frame;

e. first linkage means pivotally connected between said first frame andsaid head section whereby the longitudinal position of said mattresssupport frame is varied in accordance with the inclination of said headsection so that the head end of said head section remains in asubstantially constant longitudinal position relative to the first frameat any inclination of said head section;

f. second linkage means fastened to said head section below the plane ofsaid head section;

g. a first actuator operatively connected to said second linkage meansfor pivoting the head section relative to said seat section; and

h. a first actuator support means pivotally supporting said firstactuator whereby said first actuator is permitted to pivot about an axisto accommodate variations in height of said second linkage means as theinclination of the head section is varied.

2. A hospital bed as claimed in claim 1 wherein said first actuatorcomprises:

i. a reversible electric motor;

ii. a reduction gearbox coupled to said electric motor and having athreaded output shaft;

iii. a nut threadably engaged on said output shaft;

iv. a rod fixed at one end to said nut, said rod being driven linearlyby said nut upon actuation of said motor, said rod being pivotallyconnected at its opposite end to said second linkage means; and

v. control means including a switch for actuating said motor.

3. A hospital bed as claimed in claim 1 wherein said means for slidablysupporting said mattress support frame comprises:

i. a pair of elongated U-sectioned tracks respectively secured to theinner sides of the said longitudinal members of said first frame;

ii. a second frame having longitudinal side members;

iii. at least two rollers rotatably mounted on each of said sidemembers, said rollers being confined within said U- sectioned tracks andmovably supporting said second frame to move longitudinally relative tosaid first frame.

4. A hospital bed as claimed in claim 1 wherein said first linkage meanscomprises a pair of radius arms, each of said radius arms beingpivotally attached at one end to the head end of said first frame and atthe opposite end to said head section at points intermediate thetransversely extending ends of said head section.

5. A hospital bed as claimed in claim 1 wherein the second linkage meanscomprises: a pair of opposed brackets rigidly attached to the respectiveopposite sides of said head section adjacent said seat section; atransversely extending bar fixed to said plates below said head section;a crank fixed at one end to said bar, and extending downwardly from thebar; a pivot pin attached to the other end of said bar; and said rod ofsaid first actuator having a slot accommodating said pin for slidingmovement therein longitudinally of said rod.

6. A hospital bed as claimed in claim 1 which further comprises apivotal support frame for supporting said head section with the headsection in a generally horizontal position, said pivotal support framecomprising: a transversely extending elongated first portion upon whichsaid head section rests; a pair of opposed second portions extendingfrom the ends of said first portion and pivotally attached to said firstframe near the head end thereof; stop means for holding said pivotalsupport frame in a position in which said second portions are generallyvertical and said first portion is substantially horizontal; and ahandle attached to one of said second portions for rotating said pivotalsupport frame out of engagement with said head section to thereby permitsaid head section to be lowered.

7. A hospital bed as claimed in claim 1 wherein said axis of said firstactuator support means is transverse to the longitudinal axis of thebed.

8. A hospital bed as claimed in claim 4 wherein the second linkage meanscomprises: a pair of opposed brackets rigidly attached to the respectiveopposite sides of said head section adjacent said seat section; atransversely extending bar fixed to said plates below said head section;a crank fixed at one end to said bar, and extending downwardly from thebar; a pivot pin attached to the other end of said bar; and said rod ofsaid first actuator having a slot accommodating said pin for slidingmovementtherein longitudinally of said rod.

9. A hospital bed as claimed in claim 2 wherein said second linkagemeans comprises: a pair of opposed brackets rigidly attached to therespective opposite sides of said head section adjacent said seatsection; a transversely extending bar fixed to said plates below saidhead section; a crank fixed at one end to said bar, and extendingdownwardly from the bar; a pivot pin attached at its other end; and saidrod of said first actuator having a slot accommodating said pin forsliding movement therein longitudinally of said rod.

10. A hospital bed as claimed in claim 9 wherein said first linkagemeans comprises: a pair of radius arms, each of said radius arms beingpivotally attached at one end to the head end of said first frame and attheir opposite ends to said head section at points intermediate thetransversely extending ends of said head section.

11. A hospital bed as claimed in claim 10 which further comprises: apivotal support frame for supporting said head section with the headsection in a generally horizontal position, said pivotal support framecomprising: a transversely extending elongated first portion upon whichsaid head of opposed second portions extending from the ends of saidfirst portion and pivotally attached to said first frame near the headend thereof; stop means for holding said pivotal support frame in aposition in which said second portions are generally vertical and saidfirst portion is substantially horizontal; and a handle attached to oneof said second portions for rotating said pivotal support frame out ofengagement with said head section to thereby permit said head section tobe lowered.

12. A hospital bed as claimed in claim ll wherein said axis of saidfirst actuator support means is transverse to the longitudinal axis ofthe bed.

13. A hospital bed as claimed in claim 1 which further comprises: agenerally rectangular thigh section pivotally connected at a first sideto the side of said seat section remote from said head section; and agenerally rectangular foot section pivotally connected to a second sideof said thigh section parallel to said first side.

14. A hospital bed as claimed in claim 13 and which further includes asecond actuator for pivoting said thigh section relative to said seatsection, said second actuator comprising:

i. a reversible electric motor;

ii. a reduction gearbox coupled to said electric motor and having athreaded output shaft;

iii. a nut threadably engaged on said output shaft;

iv. a rod fixed at one end to said nut, said rod being driven linearlyby said nut upon actuation of said motor, said rod being operativelyconnected at its opposite end to said thigh section; and

v. control means including a switch for actuating said motor.

15. A hospital bed as claimed in claim 14 which further includes: a pairof opposed plates rigidly attached to the respective opposite sides ofsaid thigh section adjacent said seat section; a transversely extendingbar fixed to said plates below said thigh section; a crank fixed at oneend to said bar, said crank having a pivot pin coupled to its other end;said rod of said second actuator having an aperture for receiving saidpivot pin.

16. A hospital bed as claimed in claim 15 which further includes asecond actuator support means for pivotally supporting said secondactuator whereby said second actuator is permitted to pivot about anaxis to accommodate variations in height of said crank as theinclination of said thigh section is varied.

17. A hospital bed as claimed in claim 16 which further includes asupport for said foot section, said support comprising: a pair ofspaced-apart parallel bars having a first end pivotally attached to theunderside of said foot section adjacent said thigh section, each of saidbars having a roller rotatably attached at the other end of said barsfor rolling on an upper surface of one of said longitudinal members,said parallel bars extending from said first end downwardly and towardssaid foot portion, and each of said bars having a series of notchesalong an upwardly facing edge; a generally U-shaped notch-engagingmember having legs with free ends and a straight portion between saidlegs, said notch-engaging member being pivotally connected at its freeends to the sides of said foot section at substantially the longitudinalcenter of said sides of said foot section, said straight portion of saidnotch-engaging member being adapted to releasably fit into said notchesto retain said foot section at a predetermined angle to said thighsection.

18. A hospital bed as claimed in claim 2 wherein said rod is providedwith a pair of spaced-apart stops which are adjustably attached to saidrod, said stops being positioned to operate said switch when said headsection reaches predetermined limits of travel.

19. A hospital bed comprising:

a. a first frame having head and foot ends and parallel,

spaced-apart longitudinal members;

b. means supporting said frame above a floor and parallel thereto;

c. a mattress support frame having a head section and a seat section,said head section being pivotally connected to said seat section;

d. means slidably supporting said mattress support frame above saidfirst frame, said supporting means being adapted to permit said mattresssupport frame to slide longitudinally relative to said first frame;

. first linkage means pivotally connected between said first frame andsaid head section whereby the longitudinal position of said mattresssupport frame is varied in accordance with the inclination of said headsection so that the head end of said head section remains in asubstantially constant longitudinal position relative to the first frameat any inclination of said head section; second linkage means fastenedto said head section below the plane of said head section;

g. a first actuator attached to said means for slidably supporting saidmattress support frame whereby said actuator travels longitudinally tofollow the longitudinal travel of said mattress support frame, saidfirst actuator being operatively connected to said linkage means forpivoting said head section relative to said seat section.

20. A hospital bed as claim ed in claim 19 wherein said first actuatoris pivotally supported about an axis to permit it to accommodatevariations in height of said second linkage means as the inclination ofthe head section is varied.

21. A hospital bed as claimed in claim 19 wherein said first actuatorcomprises:

i. a reversible electric motor;

ii. a reduction gearbox coupled to said electric motor and having athreaded output shaft;

iii. a nut threadably engaged on said output shaft;

iv. a rod fixed at one end to said nut, said rod being driven linearlyby said nut upon actuation of said motor, said rod being pivotallyconnected at its opposite end to said second linkage means; and

, v; control means including a switch for actuating said motor.

22. A hospital bed as claimed in claim 19 wherein said means forslidably supporting said mattress support frame comprises:

i. a pair of elongated U-sectioned tracks respectively secured to theinner sides of the said longitudinal members of said first frame;

ii. at least two rollers rotatably mounted on each of said side members,said rollers being confined within said U-section tracks and movablysupporting said second frame to move longitudinally relative to saidfirst frame.

23. A hospital bed as claimed in claim 19 wherein said first linkagemeans comprises a pair of radius arms, each of said radius arms beingpivotally attached at one end to the head end of said first frame andat. the opposite end to said head section at points intermediate thetransversely extending ends of said head section.

24. A hospital bed as claimed .in claim 19 wherein the second linkagemeans comprises: a pair of opposed brackets rigidly attached to therespective opposite sides of said head section adjacent said seatsection; a transversely extending bar fixed to said plates below saidhead section; a crank fixed at one end to said bar, and extendingdownwardly from the bar; a pivot pin attached to the other end of saidbar; and said rod of said first actuator having a slot accommodatingsaid pin for sliding movement therein longitudinally of said rod.

25. A hospital bed as claimed in claim 19 which further comprises apivotal support frame for supporting said head section with the headsection in a generally horizontal position, said pivotal support framecomprising: a transversely extending elongated first portion upon whichsaid head section rests; a pair of opposed second portions extendingfrom the ends of said first portion and pivotally attached to said firstframe near the head end thereof; stop means for holding said pivotalsupport frame in a position in which said second portions are generallyvertical and said first portion is substantially horizontal; and ahandle attached to one of said second portions for rotating saidpivotalrsupport frame out of engagement with said head section tothereby permit said head section to be lowered.

26. A hospital bed as claimed in claim 19 wherein said first actuator ispivotally supported about an axis transverse to the longitudinal axis ofthe bed to permit said first actuator to accommodate variations inheight of said second linkage means as the inclination of the headsection is varied.

27. A hospital bed as claimed in claim 23 wherein the second linkagemeans comprises: a pair of opposed brackets rigidly attached to therespective opposite sides of said head section adjacent said seatsection; a transversely extending bar fixed to said plates below saidhead section; a crank fixed at one end to said bar, andextendingdownwardly from the bar; a pivot pin attached to the other endof said bar; and said rod of said first actuator having a slotaccommodating said pin for sliding movement therein longitudinally ofsaid rod.

28. A hospital bed as claimed in claim 21 wherein said second linkagemeans comprises: a pair of opposed brackets rigidly attached to therespective-opposite sides of said head section adjacent said seatsection; a transversely extending bar fixed to said plates below saidhead section; a crank fixed at one end to said bar, and extendingdownwardly from the bar; a pivot pin attached at its other end; and saidrod of said first actuator having a slot accommodating said pin forsliding movement therein longitudinally of said rod.

29. A hospital bed as claimed in claim 28 wherein said first linkagemeans comprises: a pair of radius arms, each of said radius arms beingpivotally attached at one end to the head end of-said first frame and attheir opposite ends to said head section at points intermediate thetransversely extending ends of said head section.

30. A hospital bed as claimed in claim 29 which further comprises: apivotal support frame for supporting said head section with the headsection in a generally horizontal position, said pivotal support framecomprising: a transversely extending elongated first portion upon whichsaid head section rests; a pair of opposed second portions extendingfrom the ends of said first portion and pivotally attached to said firstframe near the head end thereof; stop means for holding said pivotalsupport frame in a position in which said second portions are generallyvertical and said first portion is substantially horizontal; and ahandle attached to one of said second portions for rotating said pivotalsupport frame out of engagement with said head section to thereby permitsaid head section to be lowered.

31. A hospital bed as claimed in claim 19 which further comprises agenerally rectangular thigh section pivotally connected at a first sideto the side of said seat section remote from said head section; and agenerally rectangular foot section pivotally connected to a second sideof said thigh section parallel to said first side.

32. A hospital bed as claimed in claim 31 and which further includes asecond actuator for pivoting said thigh section relative to said seatsection, said second actuator comprising:

i. a reversible electric motor;

ii. a reduction gearbox coupled to said electric motor and having athreaded output shaft;

iii. a nut threadably engaged on said output shaft;

iv. a rod fixed at one end to said nut, said rod being driven linearlyby said nut upon actuation of said motor, said rod being operativelyconnected at its opposite end to said thigh section; and

v. control means including a switch for actuating said motor.

33. A hospital bed as claimed in claim 32 which further includes: a pairof opposed plates rigidly attached to the respective opposite sides ofsaid thigh section adjacent said seat sections; a transversely extendingbar fixed to said plates below said thigh section; a crank fixed at oneend to said bar, said crankhaving a pivot pin coupled to its other end;said rod of said second actuator having an aperture for receiving saidpivot pin.

34. A hospital bed as claimed in claim 33 which further includes asecond actuator support means for pivotally supporting said secondactuator whereby said second actuator is permitted to pivot about anaxis to accommodate variations in height of said crank as theinclination of said thigh section is varied.

35. A hospital bed as claimed in claim 34 which further includes asupport for said foot section, said support comprising a pair ofspaced-apart parallel bars having a first end pivotally attached to theunderside of said foot section adjacent said thigh section, each of saidbars having a roller rotatably attached at the other end of said barsfor rolling on an upper sur face of one of said longitudinal members,said parallel bars extending from said first and downwardly towards saidfoot portion, and each of said bars having a series of notches along anupwardly facing edge; a generally U-shaped notch-engaging member havinglegs with free ends and a straight portion between said legs, saidnotch-engaging member being pivotally connected at its free ends to thesides of said foot section at substantially the longitudinal center ofsaid sides of said foot section, said straight portion of saidnotch-engaging member being adapted to releasably fit into said notchesto retain said foot section at a predetermined angle to said thighsection.

36. A hospital bed as claimed in claim 21 wherein said rod is providedwith a pair of spaced-apart stops which are adjustably attached to saidrod, said stops being positioned to operate said switch when said headsection reaches predetermined limits of travel.

37. A hospital bed as claimed in claim 1 wherein said first frame ismovable between an uppermost position and a lowermost position, and saidmeans for supporting said frame above a floor and parallel theretocomprises:

a. a lower frame;

b. first and second link means pivotally connected to said lower frameand said first frame on mutually parallel sets of axes, said axesincluding a first pair of parallel axes containing pivot points at whichsaid first and second links are connected to said first frame, saidfirst and second link means being adapted to maintain said first framesubstantially parallel to said lower frame in any position of said firstframe between said uppermost and lowermost positions;

c. a crank fixed to one of said first and second link means, said crankhaving an end which is positioned such that when said first crank frameis in said uppermost position, said end is above a plane containing saidfirst pair ofaxes;

d. a second actuator means operatively connected to said end of saidcrank for pivoting said first and second link means, to thereby adjustthe height of said first frame relative to said lower frame.

38. A hospital bed as claimed in claim 37 which further includes asecond support means for pivotally supporting said second actuator onsaid first frame, whereby said second actuator is permitted to pivotabout an axis to accommodate variations in height of said crank.

39. A hospital bed as claimed in claim 38 wherein said second actuatorcomprises:

i. a reversible electric motor;

ii. a reduction gearbox coupled to said electric motor and having athreaded output shaft;

iii. a nut threadably engaged on said output shaft;

iv. a rod fixed at one end to said nut, said rod being driven linearlyby said nut upon actuation of said motor, said rod being pivotallyconnected at its opposite end to said crank; and

v. control means including a switch for actuating said motor.

40. A hospital bed as claimed in claim 19 wherein said first frame ismovable between an uppermost position and a lowermost position, and saidmeans for supporting said frame above a fioor and parallel theretocomprises:

a. a lower frame;

b. first and second link means pivotally connected to said lower frameand said first frame on mutually parallel sets of axes, said axesincluding a first pair of parallel axes containing pivot points at whichsaid first and second link means are connected to said first frame, saidfirst and second link means being adapted to maintain said first framesubstantially parallel to said lower frame in any position of said firstframe between said uppermost and lowermost positions;

. a crank fixed to one of said first and second link means, said crankhaving an end which is positioned such that when said first frame is insaid uppermost position, said end is above a plane containing said firstpair of axes; and

d. a second actuator means operatively connected to said end of saidcrank for pivoting said first and second link means, to thereby adjustthe height of said first frame relative to said lower frame.

41. A hospital bed as claimed in claim 40 which further includes asecond actuator support means for pivotally supporting said secondactuator on said first frame whereby said second actuator is permittedto pivot about an axis to accomcrank; and v. control means including aswitch for actuating said motor.

43. A hospital bed of adjustable height comprising:

a. a lower frame;

b. a first frame, said first frame being movable between an uppermostposition and a lowermost position;

c. first and second link means pivotally connected to said lower frameand said first frame on mutually parallel sets of axes, said axesincluding a first pair of parallel axes containing pivot points at whichsaid first and second link means are connected to said first frame, saidfirst and second link means being adapted to maintain said first framesubstantially parallel to said lower frame in any position of said firstframe between said uppermost and lowermost positions;

d. a crank fixed to one of said first and second link means, said crankhaving an end which is positioned such that when said first frame is insaid uppermost position, said end is above a plane containing said firstpair of axes;

e. actuator means operatively connected to said end of said cranks forpivoting said first and second link means to thereby adjust the heightof said first frame relative to said lower frame; and

f. actuator support means pivotally supporting said actuator on saidfirst frame, said actuator being coupled only to said actuator supportmeans and to said end of said cranks so that said actuator is permittedto pivot about an axis to accommodate variations in height of said crankas the first and second link means are pivoted.

44. A hospital bed of adjustable height is claimed in claim 43 whereinsaid actuator means comprises:

i. a reversible electric motor;

ii. a reduction gearbox coupled to said electric motor and having athreaded output shaft;

iii. a not threadable engaged on said output shaft;

iv. a rod fixed at one end to said nut, said rod being driven linearlyby said nut upon actuation of said motor, said rod being pivotallyconnected at its opposite end to said crank; and v. control meansincluding a switch for actuating said motor.

45. A hospital bed as claimed in claim 19 which further includes ahigh-low mechanism for adjusting the height of said first frame betweenan uppermost position and a lowermost position, said high-low mechanismcomprising:

a. a lower frame;

b. first and second link means pivotally connected to said lower frameand said first frame on mutually parallel sets of axes, said axesincluding a first pair of parallel axes containing pivot points at whichsaid first and second link means are connected to first frame, saidfirst and second link means being adapted to maintain said first framesubstantially parallel to said lower frame in any position of said firstframe between said uppermost and lowermost positions;

0. a crank fixed to one of said first and second link means, said crankhaving an end which is positioned such that when said first frame is insaid uppermost position, said end is above a plane containing said firstpair of axes;

d. a second actuator means operatively connected to said end of saidcranks for pivoting said first and second link second actuator ispermitted to pivot about an axis to accommodate variations in height ofsaid crank as the first and second link means are pi oted.

1. A hospital bed comprising: a. a first frame having head and foot endsand parallel, spacedapart longitudinal members; b. means supporting saidframe above a floor and parallel thereto; c. a mattress support framehaving a head section and a seat section, said head section beingpivotally connected to said seat section; d. means slidably supportingsaid mattress support frame above said first frame, said supportingmeans being adapted to permit said mattress support frame to slidelongitudinally relative to said first frame; e. first linkage meanspivotally connected between said first frame and said head sectionwhereby the longitudinal position of said mattress support frame isvaried in accordance with the inclination of said head section so thatthe head end of said head section remains in a substantially constantlongitudinal position relative to the first frame at any inclination ofsaid head section; f. second linkage means fastened to said head sectionbelow the plane of said head section; g. a first actuator operativelyconnected to said second linkage means for pivoting the head sectionrelative to said seat section; and h. a first actuator support meanspivotally supporting said first actuator whereby said first actuator ispermitted to pivot about an axis to accommodate variations in height ofsaid second linkage means as the inclination of the head section isvaried.
 2. A hospital bed as claimed in claim 1 wherein said firstactuator comprises: i. a reversible electric motor; ii. a reductiongearbox coupled to said electric motor and having a threaded outputshaft; iii. a nut threadably engaged on said output shaft; iv. a rodfixed at one end to said nut, said rod being driven linearly by said nutupon actuation of said motor, said rod being pivotally connected at itsopposite end to said second linkage means; and v. control meansincluding a switch for actuating said motor.
 3. A hospital bed asclaimed in claim 1 wherein said means for slidably supporting saidmattress support frame comprises: i. a pair of elongated U-sectionedtracks respectively secured to the inner sides of the said longitudinalmembers of said first frame; ii. a second frame having longitudinal sidemembers; iii. at least two rollers rotatably mounted on each of saidside members, said rollers being confined within said U-sectioned tracksand movably supporting said second frame to move longitudinally relativeto said first frame.
 4. A hospital bed as claimed in claim 1 whereinsaid first linkage means comprises a pair of radius arms, each of saidradius arms being pivotally attached at one end to the head end of saidfirst frame and at the opposite end to said head section at pointsintermediate the transversely extending ends of said head section.
 5. Ahospital bed as claimed in claim 1 wherein the second linkage meanscomprises: a pair of opposed brackets rigidly attached to the respectiveopposite sides of said head section adjacent said seat section; atransversely extending bar fixed to said plates below said head section;a crank fixed at one end to said bar, and extending downwardly from thebar; a pivot pin attached to the other end of said bar; and said rod ofsaid first actuator having a slot accommodating said pin for slidingmovement therein longitudinally of said rod.
 6. A hospital bed asclaimed in claim 1 which further comprises a pivotal support frame forsupporting said head section with the head section in a generallyhorizontal position, said pivotal support frame comprising: atransversely extending elongated first portion upon which said headsection rests; a pair of opposed second portions extending from the endsof said first portion and pivotally attached to said first frame nearthe head end thereof; stop means for holding said pivotal support framein a position in which said second portions are generally vertical andsaid first portion is substantially horizontal; and a handle attached toone of said second portions for rotating said pivotal support frame outof engagement with said head section to thereby permit said head sectionto be lowered.
 7. A hospital bed as claimed in claim 1 wherein said axisof said first actuator sUpport means is transverse to the longitudinalaxis of the bed.
 8. A hospital bed as claimed in claim 4 wherein thesecond linkage means comprises: a pair of opposed brackets rigidlyattached to the respective opposite sides of said head section adjacentsaid seat section; a transversely extending bar fixed to said platesbelow said head section; a crank fixed at one end to said bar, andextending downwardly from the bar; a pivot pin attached to the other endof said bar; and said rod of said first actuator having a slotaccommodating said pin for sliding movement therein longitudinally ofsaid rod.
 9. A hospital bed as claimed in claim 2 wherein said secondlinkage means comprises: a pair of opposed brackets rigidly attached tothe respective opposite sides of said head section adjacent said seatsection; a transversely extending bar fixed to said plates below saidhead section; a crank fixed at one end to said bar, and extendingdownwardly from the bar; a pivot pin attached at its other end; and saidrod of said first actuator having a slot accommodating said pin forsliding movement therein longitudinally of said rod.
 10. A hospital bedas claimed in claim 9 wherein said first linkage means comprises: a pairof radius arms, each of said radius arms being pivotally attached at oneend to the head end of said first frame and at their opposite ends tosaid head section at points intermediate the transversely extending endsof said head section.
 11. A hospital bed as claimed in claim 10 whichfurther comprises: a pivotal support frame for supporting said headsection with the head section in a generally horizontal position, saidpivotal support frame comprising: a transversely extending elongatedfirst portion upon which said head of opposed second portions extendingfrom the ends of said first portion and pivotally attached to said firstframe near the head end thereof; stop means for holding said pivotalsupport frame in a position in which said second portions are generallyvertical and said first portion is substantially horizontal; and ahandle attached to one of said second portions for rotating said pivotalsupport frame out of engagement with said head section to thereby permitsaid head section to be lowered.
 12. A hospital bed as claimed in claim11 wherein said axis of said first actuator support means is transverseto the longitudinal axis of the bed.
 13. A hospital bed as claimed inclaim 1 which further comprises: a generally rectangular thigh sectionpivotally connected at a first side to the side of said seat sectionremote from said head section; and a generally rectangular foot sectionpivotally connected to a second side of said thigh section parallel tosaid first side.
 14. A hospital bed as claimed in claim 13 and whichfurther includes a second actuator for pivoting said thigh sectionrelative to said seat section, said second actuator comprising: i. areversible electric motor; ii. a reduction gearbox coupled to saidelectric motor and having a threaded output shaft; iii. a nut threadablyengaged on said output shaft; iv. a rod fixed at one end to said nut,said rod being driven linearly by said nut upon actuation of said motor,said rod being operatively connected at its opposite end to said thighsection; and v. control means including a switch for actuating saidmotor.
 15. A hospital bed as claimed in claim 14 which further includes:a pair of opposed plates rigidly attached to the respective oppositesides of said thigh section adjacent said seat section; a transverselyextending bar fixed to said plates below said thigh section; a crankfixed at one end to said bar, said crank having a pivot pin coupled toits other end; said rod of said second actuator having an aperture forreceiving said pivot pin.
 16. A hospital bed as claimed in claim 15which further includes a second actuator support means for pivotallysupporting said second actuator whereby said second actuator ispermitted to pivot about an axis to accommodate variations in height ofsaid crank as the inclination of said thigh section is varied.
 17. Ahospital bed as claimed in claim 16 which further includes a support forsaid foot section, said support comprising: a pair of spaced-apartparallel bars having a first end pivotally attached to the underside ofsaid foot section adjacent said thigh section, each of said bars havinga roller rotatably attached at the other end of said bars for rolling onan upper surface of one of said longitudinal members, said parallel barsextending from said first end downwardly and towards said foot portion,and each of said bars having a series of notches along an upwardlyfacing edge; a generally U-shaped notch-engaging member having legs withfree ends and a straight portion between said legs, said notch-engagingmember being pivotally connected at its free ends to the sides of saidfoot section at substantially the longitudinal center of said sides ofsaid foot section, said straight portion of said notch-engaging memberbeing adapted to releasably fit into said notches to retain said footsection at a predetermined angle to said thigh section.
 18. A hospitalbed as claimed in claim 2 wherein said rod is provided with a pair ofspaced-apart stops which are adjustably attached to said rod, said stopsbeing positioned to operate said switch when said head section reachespredetermined limits of travel.
 19. A hospital bed comprising: a. afirst frame having head and foot ends and parallel, spaced-apartlongitudinal members; b. means supporting said frame above a floor andparallel thereto; c. a mattress support frame having a head section anda seat section, said head section being pivotally connected to said seatsection; d. means slidably supporting said mattress support frame abovesaid first frame, said supporting means being adapted to permit saidmattress support frame to slide longitudinally relative to said firstframe; e. first linkage means pivotally connected between said firstframe and said head section whereby the longitudinal position of saidmattress support frame is varied in accordance with the inclination ofsaid head section so that the head end of said head section remains in asubstantially constant longitudinal position relative to the first frameat any inclination of said head section; f. second linkage meansfastened to said head section below the plane of said head section; g. afirst actuator attached to said means for slidably supporting saidmattress support frame whereby said actuator travels longitudinally tofollow the longitudinal travel of said mattress support frame, saidfirst actuator being operatively connected to said linkage means forpivoting said head section relative to said seat section.
 20. A hospitalbed as claimed in claim 19 wherein said first actuator is pivotallysupported about an axis to permit it to accommodate variations in heightof said second linkage means as the inclination of the head section isvaried.
 21. A hospital bed as claimed in claim 19 wherein said firstactuator comprises: i. a reversible electric motor; ii. a reductiongearbox coupled to said electric motor and having a threaded outputshaft; iii. a nut threadably engaged on said output shaft; iv. a rodfixed at one end to said nut, said rod being driven linearly by said nutupon actuation of said motor, said rod being pivotally connected at itsopposite end to said second linkage means; and v. control meansincluding a switch for actuating said motor.
 22. A hospital bed asclaimed in claim 19 wherein said means for slidably supporting saidmattress support frame comprises: i. a pair of elongated U-sectionedtracks respectively secured to the inner sides of the said longitudinalmembers of said first frame; ii. at least two rollers rotatably mountedon each of said side members, said rollers being confined within saidU-section tracks and movably suppoRting said second frame to movelongitudinally relative to said first frame.
 23. A hospital bed asclaimed in claim 19 wherein said first linkage means comprises a pair ofradius arms, each of said radius arms being pivotally attached at oneend to the head end of said first frame and at the opposite end to saidhead section at points intermediate the transversely extending ends ofsaid head section.
 24. A hospital bed as claimed in claim 19 wherein thesecond linkage means comprises: a pair of opposed brackets rigidlyattached to the respective opposite sides of said head section adjacentsaid seat section; a transversely extending bar fixed to said platesbelow said head section; a crank fixed at one end to said bar, andextending downwardly from the bar; a pivot pin attached to the other endof said bar; and said rod of said first actuator having a slotaccommodating said pin for sliding movement therein longitudinally ofsaid rod.
 25. A hospital bed as claimed in claim 19 which furthercomprises a pivotal support frame for supporting said head section withthe head section in a generally horizontal position, said pivotalsupport frame comprising: a transversely extending elongated firstportion upon which said head section rests; a pair of opposed secondportions extending from the ends of said first portion and pivotallyattached to said first frame near the head end thereof; stop means forholding said pivotal support frame in a position in which said secondportions are generally vertical and said first portion is substantiallyhorizontal; and a handle attached to one of said second portions forrotating said pivotal support frame out of engagement with said headsection to thereby permit said head section to be lowered.
 26. Ahospital bed as claimed in claim 19 wherein said first actuator ispivotally supported about an axis transverse to the longitudinal axis ofthe bed to permit said first actuator to accommodate variations inheight of said second linkage means as the inclination of the headsection is varied.
 27. A hospital bed as claimed in claim 23 wherein thesecond linkage means comprises: a pair of opposed brackets rigidlyattached to the respective opposite sides of said head section adjacentsaid seat section; a transversely extending bar fixed to said platesbelow said head section; a crank fixed at one end to said bar, andextending downwardly from the bar; a pivot pin attached to the other endof said bar; and said rod of said first actuator having a slotaccommodating said pin for sliding movement therein longitudinally ofsaid rod.
 28. A hospital bed as claimed in claim 21 wherein said secondlinkage means comprises: a pair of opposed brackets rigidly attached tothe respective opposite sides of said head section adjacent said seatsection; a transversely extending bar fixed to said plates below saidhead section; a crank fixed at one end to said bar, and extendingdownwardly from the bar; a pivot pin attached at its other end; and saidrod of said first actuator having a slot accommodating said pin forsliding movement therein longitudinally of said rod.
 29. A hospital bedas claimed in claim 28 wherein said first linkage means comprises: apair of radius arms, each of said radius arms being pivotally attachedat one end to the head end of said first frame and at their oppositeends to said head section at points intermediate the transverselyextending ends of said head section.
 30. A hospital bed as claimed inclaim 29 which further comprises: a pivotal support frame for supportingsaid head section with the head section in a generally horizontalposition, said pivotal support frame comprising: a transverselyextending elongated first portion upon which said head section rests; apair of opposed second portions extending from the ends of said firstportion and pivotally attached to said first frame near the head endthereof; stop means for holding said pivotal support frame in a positionin which said second portions aRe generally vertical and said firstportion is substantially horizontal; and a handle attached to one ofsaid second portions for rotating said pivotal support frame out ofengagement with said head section to thereby permit said head section tobe lowered.
 31. A hospital bed as claimed in claim 19 which furthercomprises a generally rectangular thigh section pivotally connected at afirst side to the side of said seat section remote from said headsection; and a generally rectangular foot section pivotally connected toa second side of said thigh section parallel to said first side.
 32. Ahospital bed as claimed in claim 31 and which further includes a secondactuator for pivoting said thigh section relative to said seat section,said second actuator comprising: i. a reversible electric motor; ii. areduction gearbox coupled to said electric motor and having a threadedoutput shaft; iii. a nut threadably engaged on said output shaft; iv. arod fixed at one end to said nut, said rod being driven linearly by saidnut upon actuation of said motor, said rod being operatively connectedat its opposite end to said thigh section; and v. control meansincluding a switch for actuating said motor.
 33. A hospital bed asclaimed in claim 32 which further includes: a pair of opposed platesrigidly attached to the respective opposite sides of said thigh sectionadjacent said seat sections; a transversely extending bar fixed to saidplates below said thigh section; a crank fixed at one end to said bar,said crank having a pivot pin coupled to its other end; said rod of saidsecond actuator having an aperture for receiving said pivot pin.
 34. Ahospital bed as claimed in claim 33 which further includes a secondactuator support means for pivotally supporting said second actuatorwhereby said second actuator is permitted to pivot about an axis toaccommodate variations in height of said crank as the inclination ofsaid thigh section is varied.
 35. A hospital bed as claimed in claim 34which further includes a support for said foot section, said supportcomprising a pair of spaced-apart parallel bars having a first endpivotally attached to the underside of said foot section adjacent saidthigh section, each of said bars having a roller rotatably attached atthe other end of said bars for rolling on an upper surface of one ofsaid longitudinal members, said parallel bars extending from said firstand downwardly towards said foot portion, and each of said bars having aseries of notches along an upwardly facing edge; a generally U-shapednotch-engaging member having legs with free ends and a straight portionbetween said legs, said notch-engaging member being pivotally connectedat its free ends to the sides of said foot section at substantially thelongitudinal center of said sides of said foot section, said straightportion of said notch-engaging member being adapted to releasably fitinto said notches to retain said foot section at a predetermined angleto said thigh section.
 36. A hospital bed as claimed in claim 21 whereinsaid rod is provided with a pair of spaced-apart stops which areadjustably attached to said rod, said stops being positioned to operatesaid switch when said head section reaches predetermined limits oftravel.
 37. A hospital bed as claimed in claim 1 wherein said firstframe is movable between an uppermost position and a lowermost position,and said means for supporting said frame above a floor and parallelthereto comprises: a. a lower frame; b. first and second link meanspivotally connected to said lower frame and said first frame on mutuallyparallel sets of axes, said axes including a first pair of parallel axescontaining pivot points at which said first and second links areconnected to said first frame, said first and second link means beingadapted to maintain said first frame substantially parallel to saidlower frame in any position of said first frame between said uppermostand lowermost positions; C. a crank fixed to one of said first andsecond link means, said crank having an end which is positioned suchthat when said first crank frame is in said uppermost position, said endis above a plane containing said first pair of axes; d. a secondactuator means operatively connected to said end of said crank forpivoting said first and second link means, to thereby adjust the heightof said first frame relative to said lower frame.
 38. A hospital bed asclaimed in claim 37 which further includes a second support means forpivotally supporting said second actuator on said first frame, wherebysaid second actuator is permitted to pivot about an axis to accommodatevariations in height of said crank.
 39. A hospital bed as claimed inclaim 38 wherein said second actuator comprises: i. a reversibleelectric motor; ii. a reduction gearbox coupled to said electric motorand having a threaded output shaft; iii. a nut threadably engaged onsaid output shaft; iv. a rod fixed at one end to said nut, said rodbeing driven linearly by said nut upon actuation of said motor, said rodbeing pivotally connected at its opposite end to said crank; and v.control means including a switch for actuating said motor.
 40. Ahospital bed as claimed in claim 19 wherein said first frame is movablebetween an uppermost position and a lowermost position, and said meansfor supporting said frame above a floor and parallel thereto comprises:a. a lower frame; b. first and second link means pivotally connected tosaid lower frame and said first frame on mutually parallel sets of axes,said axes including a first pair of parallel axes containing pivotpoints at which said first and second link means are connected to saidfirst frame, said first and second link means being adapted to maintainsaid first frame substantially parallel to said lower frame in anyposition of said first frame between said uppermost and lowermostpositions; c. a crank fixed to one of said first and second link means,said crank having an end which is positioned such that when said firstframe is in said uppermost position, said end is above a planecontaining said first pair of axes; and d. a second actuator meansoperatively connected to said end of said crank for pivoting said firstand second link means, to thereby adjust the height of said first framerelative to said lower frame.
 41. A hospital bed as claimed in claim 40which further includes a second actuator support means for pivotallysupporting said second actuator on said first frame whereby said secondactuator is permitted to pivot about an axis to accommodate variationsin height of said second linkage means as the inclination of the headsection is varied.
 42. A hospital bed as claimed in claim 41 whereinsaid second actuator comprises: i. a reversible electric motor; ii. areduction gearbox coupled to said electric motor and having a threadedoutput shaft; iii. a nut threadably engaged on said output shaft; iv. arod fixed at one end to said nut, said rod being driven linearly by saidnut upon actuation of said motor, said rod being pivotally connected atits opposite end to said crank; and v. control means including a switchfor actuating said motor.
 43. A hospital bed of adjustable heightcomprising: a. a lower frame; b. a first frame, said first frame beingmovable between an uppermost position and a lowermost position; c. firstand second link means pivotally connected to said lower frame and saidfirst frame on mutually parallel sets of axes, said axes including afirst pair of parallel axes containing pivot points at which said firstand second link means are connected to said first frame, said first andsecond link means being adapted to maintain said first framesubstantially parallel to said lower frame in any position of said firstframe between said uppermost and lowermost positions; d. a crank fixedto one of said first and second link means, said crank having an endwhich is positioned such that when said first frame is in said uppermostposition, said end is above a plane containing said first pair of axes;e. actuator means operatively connected to said end of said cranks forpivoting said first and second link means to thereby adjust the heightof said first frame relative to said lower frame; and f. actuatorsupport means pivotally supporting said actuator on said first frame,said actuator being coupled only to said actuator support means and tosaid end of said cranks so that said actuator is permitted to pivotabout an axis to accommodate variations in height of said crank as thefirst and second link means are pivoted.
 44. A hospital bed ofadjustable height is claimed in claim 43 wherein said actuator meanscomprises: i. a reversible electric motor; ii. a reduction gearboxcoupled to said electric motor and having a threaded output shaft; iii.a not threadable engaged on said output shaft; iv. a rod fixed at oneend to said nut, said rod being driven linearly by said nut uponactuation of said motor, said rod being pivotally connected at itsopposite end to said crank; and v. control means including a switch foractuating said motor.
 45. A hospital bed as claimed in claim 19 whichfurther includes a high-low mechanism for adjusting the height of saidfirst frame between an uppermost position and a lowermost position, saidhigh-low mechanism comprising: a. a lower frame; b. first and secondlink means pivotally connected to said lower frame and said first frameon mutually parallel sets of axes, said axes including a first pair ofparallel axes containing pivot points at which said first and secondlink means are connected to first frame, said first and second linkmeans being adapted to maintain said first frame substantially parallelto said lower frame in any position of said first frame between saiduppermost and lowermost positions; c. a crank fixed to one of said firstand second link means, said crank having an end which is positioned suchthat when said first frame is in said uppermost position, said end isabove a plane containing said first pair of axes; d. a second actuatormeans operatively connected to said end of said cranks for pivoting saidfirst and second link means to thereby adjust the height of said firstframe relative to said lower frame; and e. a second actuator supportmeans for pivotally supporting said second actuator on said first frame,whereby said second actuator is permitted to pivot about an axis toaccommodate variations in height of said crank as the first and secondlink means are pivoted.